Windows commandline to eject a USB drive

ejectusb.py

#!/usr/bin/python3

# From DOS commandline, run this as follows:-
#        python3 ejectusb.py
# -or- create C:\windows\ejectusb.bat to do the above in fewer characters.
#
# From WSL bash, run it as follows:-
#        cmd.exe /c start python3 C:\\windows\\ejectusb.py
# -or- create /usr/local/bin/ejectusb to do the above in fewer characters.

import string
import ctypes
from ctypes import wintypes  # Using ctypes.wintypes in the code below does not seem to work


# Ignore windows error popups. Fixes the whole "Can't open drive X" when user has an SD card reader.
ctypes.windll.kernel32.SetErrorMode(1) #type: ignore

# WinAPI Constants that we need
# Hardcoded here due to stupid WinDLL stuff that does not give us access to these values.
DRIVE_REMOVABLE = 2 # [CodeStyle: Windows Enum value]

GENERIC_READ = 2147483648 # [CodeStyle: Windows Enum value]
GENERIC_WRITE = 1073741824 # [CodeStyle: Windows Enum value]

FILE_SHARE_READ = 1 # [CodeStyle: Windows Enum value]
FILE_SHARE_WRITE = 2 # [CodeStyle: Windows Enum value]

IOCTL_STORAGE_EJECT_MEDIA = 2967560 # [CodeStyle: Windows Enum value]

OPEN_EXISTING = 3 # [CodeStyle: Windows Enum value]

# Setup the DeviceIoControl function arguments and return type.
# See ctypes documentation for details on how to call C functions from python, and why this is important.
ctypes.windll.kernel32.DeviceIoControl.argtypes = [ #type: ignore
    wintypes.HANDLE,                    # _In_          HANDLE hDevice
    wintypes.DWORD,                     # _In_          DWORD dwIoControlCode
    wintypes.LPVOID,                    # _In_opt_      LPVOID lpInBuffer
    wintypes.DWORD,                     # _In_          DWORD nInBufferSize
    wintypes.LPVOID,                    # _Out_opt_     LPVOID lpOutBuffer
    wintypes.DWORD,                     # _In_          DWORD nOutBufferSize
    ctypes.POINTER(wintypes.DWORD),     # _Out_opt_     LPDWORD lpBytesReturned
    wintypes.LPVOID                     # _Inout_opt_   LPOVERLAPPED lpOverlapped
]
ctypes.windll.kernel32.DeviceIoControl.restype = wintypes.BOOL #type: ignore



def checkRemovableDrives():
    drives = {}

    # The currently available disk drives, e.g.: bitmask = ...1100 <-- ...DCBA
    bitmask = ctypes.windll.kernel32.GetLogicalDrives()
    # Since we are ignoring drives A and B, the bitmask has has to shift twice to the right
    bitmask >>= 2
    # Check possible drive letters, from C to Z
    # Note: using ascii_uppercase because we do not want this to change with locale!
    # Skip A and B, since those drives are typically reserved for floppy disks.
    # Those drives can theoretically be reassigned but it's safer to not check them for removable drives.
    # Windows will also behave weirdly even with some of its internal functions if you do this (e.g. search indexing doesn't search it).
    # Users that have removable drives in A or B will just have to save to file and select the drive there.
    for letter in string.ascii_uppercase[2:]:
        drive = "{0}:/".format(letter)

        # Do we really want to skip A and B?
        # GetDriveTypeA explicitly wants a byte array of type ascii. It will accept a string, but this wont work
        if bitmask & 1 and ctypes.windll.kernel32.GetDriveTypeA(drive.encode("ascii")) == DRIVE_REMOVABLE:
            volume_name = ""
            name_buffer = ctypes.create_unicode_buffer(1024)
            filesystem_buffer = ctypes.create_unicode_buffer(1024)
            error = ctypes.windll.kernel32.GetVolumeInformationW(ctypes.c_wchar_p(drive), name_buffer, ctypes.sizeof(name_buffer), None, None, None, filesystem_buffer, ctypes.sizeof(filesystem_buffer))

            if error != 0:
                volume_name = name_buffer.value

            if not volume_name:
                volume_name = "Removable Drive"

            # Certain readers will report themselves as a volume even when there is no card inserted, but will show an
            # "No volume in drive" warning when trying to call GetDiskFreeSpace. However, they will not report a valid
            # filesystem, so we can filter on that. In addition, this excludes other things with filesystems Windows
            # does not support.
            if filesystem_buffer.value == "":
                continue

            # Check for the free space. Some card readers show up as a drive with 0 space free when there is no card inserted.
            free_bytes = ctypes.c_longlong(0)
            if ctypes.windll.kernel32.GetDiskFreeSpaceExA(drive.encode("ascii"), ctypes.byref(free_bytes), None, None) == 0:
                continue

            if free_bytes.value < 1:
                continue

            drives[drive] = "{0} ({1}:)".format(volume_name, letter)
        bitmask >>= 1

    return drives

def performEjectDevice(device):
    # Magic WinAPI stuff
    # First, open a handle to the Device
    #handle = ctypes.windll.kernel32.CreateFileA("\\\\.\\{0}".format(device.getId()[:-1]).encode("ascii"), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, None, OPEN_EXISTING, 0, None )
    handle = ctypes.windll.kernel32.CreateFileA("\\\\.\\{0}".format(device[:-1]).encode("ascii"), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, None, OPEN_EXISTING, 0, None )
    #handle = ctypes.windll.kernel32.CreateFileA("E:/".encode("ascii"), GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, None, OPEN_EXISTING, 0, None )

    if handle == -1:
        # ctypes.WinError sets up an GetLastError API call for windows as an Python OSError exception.
        # So we use this to raise the error to our caller.
        raise ctypes.WinError()

    # The DeviceIoControl requires a bytes_returned pointer to be a valid pointer.
    # So create a ctypes DWORD to reference. (Without this pointer the DeviceIoControl function will crash with an access violation after doing its job.
    bytes_returned = wintypes.DWORD(0)

    error = None

    # Then, try and tell it to eject
    return_code = ctypes.windll.kernel32.DeviceIoControl(handle, IOCTL_STORAGE_EJECT_MEDIA, None, 0, None, 0, ctypes.pointer(bytes_returned), None)
    # DeviceIoControl with IOCTL_STORAGE_EJECT_MEDIA return 0 on error.
    if return_code == 0:
        # ctypes.WinError sets up an GetLastError API call for windows as an Python OSError exception.
        # So we use this to raise the error to our caller.
        error = ctypes.WinError()
        # Do not raise an error here yet, so we can properly close the handle.

    # Finally, close the handle
    ctypes.windll.kernel32.CloseHandle(handle)

    # If an error happened in the DeviceIoControl, raise it now.
    if error:
        raise error

    # Return success
    return True


mydrives=checkRemovableDrives()
if mydrives:
    #print(mydrives)
    for drive in mydrives:
        print("Ejecting drive {0} {1}".format(drive,mydrives[drive]))
        if performEjectDevice(drive):
            print("Success")
            exit(0)
        else:
            print("Failed")
            exit(0)
else:
    print("No removable drives")